Difluoroamine substituted-1, 3-dioxolanes



United States Patent 3,394,148 DIFLUOROAMINE SUBSTITUTED- 1,3-DIOXOLANES Robert K. Armstrong, Glassboro, and Marvin L. Peterson, Woodbury, N.J., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Sept. 6, 1961, Ser. No. 137,938 7 Claims. (Cl. 260-3403) This invention relates to dioxolanes containing difluoramino (--NF substituents and to a process for their preparation.

In recent years, the presence of difluoramino groups in a molecule has become recognized as an important source of energy, compounds containing such groups having been found to impart a high specific impulse to rocket propellants. The difluoramino-substituted dioxolanes of the present invention can contain a high percentage by weight of difluoramino groups and therefore find utility in rocket propellant formulations. The compounds of this invention can be used directly in propellant formulations, or they can be used as intermediates to other high-energy NF containing chemicals. For example, they can be used as starting materials for the high-energy compounds described in US. Patent 3,347,904, issued Oct. 17, 1967.

The compounds of the invention are 1,3-dioxolanes having an alkyl group attached to at least one of the carbon atoms of the dioxolane ring and one or more pairs of difiuoramino substituents, the two substituents of any one pair being attached to adjacent carbon atoms, at least one of which is a member of a side-chain alkyl group. The compounds contain pairs of difluoramino substituents of one or both of the following types: (1) those wherein the two substituents of the pair are attached to adjacent carbon atoms both of which are members of an alkyl sidechain attached to the dioxolane ring; and (2) those wherein the two substituents are attached to adjacent carbon atoms one of which is a member of the dioxolane ring and the other a member of an alkyl side-chain attached to the dioxolane ring. More specifically, the compounds of this invention include dioxolanes wherein one or each of two of the carbon atoms in the dioxolane ring has attached to it a difluoramino radical which is one of a pair of such radicals; as well as dioxolancs wherein one or each of two or three of the carbon atoms in the dioxolane ring has attached to it an alkyl radical containing at least one pair of difluoroamino substituents.

Accordingly, the compounds of the invention can be represented by the formula:

X1X A at wherein X X and X are independently selected, and 1 is 2) 1( 2)( Z),

or CH-(CH CR (NF )CR (R (N1 and R and R are H or a lower, e.g., 1-3 carbon, alkyl radical;

and

n is an integer from 1 to 3.

The number of carbon atoms in the alkyl group(s) of the compounds can be varied widely. However, since a high NFg/C ratio is desirable for propellant ingredients, the preferred compounds for propellants are those containing but few carbon atoms in the alkyl(s) in addition to those carbon atoms to which difiuoramino radicals are attached. From the point of view of suitability for propellants, any of the difiuoramino-substituted dioxolanes are of interest regardless of number of carbon atoms in the side-chain(s) so long as the NF /C ratio is at least about 2/3. For reasons of availability of starting materials, the preferred dioxolanes of this invention are those having one to four carbon atoms per alkyl group.

Typical examples of the dioxolanes having substitution on only one ring carbon atom are 2(or 4)-difluoramino- 2(or 4)-difluoraminomethyl-1,3-dioxolane; 2(or 4)-[1,2- bis(difluoramino)ethyl]-1,3-dioxolane; 2(or 4)-[2,3-bis- (difluoramino)propyl]-1,3-dioxolane; 2(or 4)-[3,4-bis(difiuoramino)butyl]-1,3-dioxolane; and derivatives of these compounds wherein one or more of the hydrogen atoms are replaced by a lower alkyl (i.e., a 1-3 carbon) group. Dioxolanes substituted on two ring carbon atoms include, for example, 4,5 (or 2,4)-bis(difluoramino)-4,5 (or 2,4)- bis (difluoraminomethyl)-1,3-dioxolane; 4,5(or 2,4)-bis [1,2-bis(difluorarnino) ethyl] 1,3-dioXolane; 4,5(or 2,4)- bis [2,3 bis(difluoramino)propyl] 1,3 dioxolane; 4,5(or 2,4) -bis-[3,4-bis (difluoramino) butyl] -1,3-dioxolane; 2-difluoramino-2-difluoraminomethyl 4 [1,2 bis(difluoramino)ethyl]-1,3-dioxolane; and derivatives of these compounds wherein one or more of the hydrogen atoms are replaced by a lower alkyl (i.e., a 1-3 carbon) group. All three carbon atoms of the dioxolane ring may be substituted, as, for example, in 2,4,5-tris[1,2-bis(difiuoramino) ethyl]-l,3-dioxolane and derivatives thereof wherein one or more of the hydrogen atoms in the alkyl side chains are replaced by a lower alkyl (Le, a l-3 carbon) group. The alkyl side chains in the above compounds also can contain additional pairs of difiuoramino substituents.

The difluoramino-subs-tituted dioxolanes of the invention are prepared by reacting tetrafluorohydrazine with a 1,3-dioxolane having at least one hydrocarbon side-chain and at least one exocyclic olefinic double bond. By exocyclic olefinic double bond we mean an olefinic double bond situated outside the dioxolane ring. Equally suitable starting materials are 1,3-dioxolanes having at least one hydrocarbon side-chain wherein an olefinic double bond joins a carbon atom in the dioxolane ring in a side-chain carbon atom, as well as those wherein the double bond joins two side-chain carbon atoms. Such olefinic compounds may be represented by the following formula:

0\ /0 X3 wherein:

R and R are H or a lower, e.g., 1-3 carbon, alkyl radical;

and n is an integer from 1 to 3.

The reaction of tetrafiuorohydrazine with a 1,3-dioxolane having at least one hydrocarbon side-chain and at least one exocyclic olefinic double bond to give the difluoramino-substituted 1,3-dioxolanes of the invention can be effected either in the liquid or vapor phase. When the reaction is carried out in the liquid phase, an inert diluent preferably is used in conjunction with the olefinic compound in order to increase fluidity and to help dissipate any heat of reaction. The diluent can be any liquid which is not reactive with the reaction components under the conditions used. Preferably, the diluent is not too highboiling so that it can be removed easily from the reaction product. Compounds which are particularly useful as diluents are the halogenated hydrocarbons, e.g., chloroform, methylene chloride, and chlorofluoro hydrocarbons such as 1,1,2-trichloro-1,2,2-trifiuoroethane.

The temperature at which the reaction between tetrafiuorohydrazine and olefinic compound is effected will vary according to other reaction variables but in general will be within the range from about 75 C. to about 250 C. Generally, when it is desired to operate at the lower end of the temperature range, e.g., at 75125 C., the reaction will be carried out in the liquid phase since such a procedure more conveniently provides a longer contact time than a vapor-phase procedure. If it is desired to operate in the upper ranges, e.g., at 125250 C., a vaporphase procedure is more suitable, these temperatures being suflicient to provide the desired reaction at the shorter contact times. Possible decomposition of the product at the higher temperatures is avoided in the vapor-phase procedure by rapid removal of the product from the reaction zone.

The process for preparing the compounds of the invention can be effected at atmospheric as well as superatmospheric pressure. For operation in the liquid phase, the use of superatmospheric pressure, for example at least about 70 p.s.i.ga., is desirable in order to achieve a reasonably high reaction rate and to prevent any low-boiling solvent from vaporizing. Pressures as high as 500 p.s.i.g. and above can be used in liquid-phase reactions, although generally there is no advantage in operating at pressures much above 500 p.s.i.g. For operation in the vapor phase, the use of atmospheric pressure is entirely adequate; in this mode of operation, elevated pressures are unnecessary and generally are not preferred.

The reactant ratios used are not critical to the present process although the tetrafluorohydrazine preferably is used in stoichiometric excess of that required to add the pair of difiuor-amino groups to the desired number of olefinic double bonds.

The substituted dioxolanes can be recovered from liquid reaction mixtures by distillation, preferably under vacuum. At the same time, any diluent present is thereby removed.

The following examples illustrate preferred methods of preparing compounds of the invention. Parts are by weight. The examples will be understood to be illustrative only and not to limit the invention in any manner.

Example 1 Tetrafluorohydrazine (F N-NF under an initial pressure of 80 p.s.i.g. was introduced into a solution of 4.3 parts of 4-methylene-1,3-dioxolane in 112 parts of chloroform, and the mixture was heated to 100 C. The pressure rose to a maximum of 102 p.s.i.g. After 30 minutes of heating, the reaction mixture was cooled to room tem-" perature, whereupon the pressure had dropped to 60 p.s.i.g. The yellow solution was removed from the reactor, and the chloroform was distilled off. The remaining liquid was distilled in vacuo to give 4.1 parts of a colorless liquid boiling at 57-58 C. at mm. The liquid was identified as 4-difiuoramino-4-(difluoraminomethyl)-1,3-dioxolane,

The infrared spectrum for the compound showed characteristic absorption peaks at 3.45 (C-H absorption);

4 6.8a, 7.0 and 7.15 (C-C absorption); 9.1; (C-O absorption); and 11.3, and 12.2 (NF absorption). The fluorine resonance spectrum showed the presence of CH NF and CNF Example 2 Tetrafluorohydrazine under an initial pressure of p.s.i.g. was introduced into a solution of 5.0 parts of 4-vinyl-1,3-dioxolane in 112 parts of chloroform, and the mixture was heated to C. The reaction was completed in 30 minutes as evidenced by the fact that there was no further drop in pressure. After cooling, the reaction mixture was distilled to give 6.1 parts of a colorless liquid boiling at 45 C. at 1 mm. The liquid was identified as 4-[1,2-bis(difiuoramino)ethyl]-1,3-dioxolane, i.e.:

The infrared spectrum of the compound showed --NF absorption at 10.6 11.5;/., 11.9,u, and 12.4 and dioxolane ring absorption at 9.1a. There was no C=C absorption at 6.06.1/.L as there had been in the spectrum of the vinyl compound used as the starting material.

Example 3 Tetrafluorohydrazine under an initial pressure of 76 p.s.i.g. was introduced into a solution of 6.3 parts of 4,5-divinyl-1,3-dioxolane in 112 parts of chloroform, and the mixture was heated to 100 C. The reaction was completed in 2.5 hours (i.e., no further pressure drop), after which time the reaction mixture was cooled and then distilled to give 10.5 parts of a colorless liquid boiling at 7578 C. at 0.2 mm. The liquid was identified as 4,5- bis-[ 1,2-bis(difiuorarnino ethyl] -1,3-dioxolane, i.e.:

The infrared spectrum of the compound showed intense broad bands in the -NF absorption region at 10.2- 10.4 4, 11.7 1l.9 and 12.4].L, the greater intensity indicating a greater number of NF groups than in the compound of Example 2; and dioxolane ring absorption at 9.1 There were no -C:C- bands at 6.1,u, 10.1,LL, and 10.7;4 as there had been in the divinyl compound used as the starting material.

Example 4 Tetrafluorohydrazine under an initial pressure of 85 p.s.i.ga. was introduced into a solution of 4.56 parts of 2,4,5-trivinyl 1,3-dioxolane in 112 parts of chloroform, and the mixture was heated at 100 C. for 3.5 hours. Distillation of the reaction product gave 1.0 part of a colorless liquid boiling at 100109 C. at 0.20 mm. and identified as 2, 4,5-tris-['1,2-bis(difluoramino)-ethyl]-1,3- dioxolane, i.e.:

The infrared spectrum of the compound showed intense broad bands in the -NF absorption region at 10.3 1 1.5 and 12.2,u (more intense than those in the spectrum of the compound of Example 3, indicating more NF groups);

and dioxolane ring absorption at 9.1,u. There was no -C=C absorption.

Example 5 4-rnethylene 1,3 dioxolane and tetrafluorohydrazine were passed concurrently through a tube heated to 150 C. at flow rates of 6.1 parts per hour and 8.4 parts per hour, respectively. The gases leaving the tube were condensed to give a dark-red liquid. The liquid product which had been collected after 30 minutes was distilled to give 3 parts of a colorless liquid boiling at 47-48" C. at 7 mm.

Example 6 4-vinyl-1,3-dioxolane and tetrazfiuorohydrazine were passed concurrently through a tube heated to 175 C. t flow rates of 6.2 parts per hour and 6.8 parts per hour, respectively. The gases leaving the tube were condensed to give a pale-yellow liquid. The liquid which had been collected after 30 minutes was distilled to give 2.5 parts of a colorless liquid boiling at 35-3'6" C. at 0.2-0.3 mm. The liquid was identified as 4-[1,2-bis-(difluoramino) ethyl]-1,3-dioxolane. The infrared spectrum showed absorption at 3.4 3.5n (C-H stretch); 6.8,u and 7.0# (C-C stretch); and 11.4 12.0 and 12.5,u. (-NF group). The fluorine and proton resonance spectra showed the presence of CH O-,

The compounds prepared in Examples 2, 3, and 4 were tested for sensitivity to heat, impact, and electrical charges. When heated gradually (ca. C./minute) in a copper block, all three compounds boiled and fumed at 250 C., but did not ignite or detonate. The impact sensitivities were measured by dropping a l-kg. weight onto the compounds. The distance the weight had to drop to produce explosion in 50% of the trials was 11.5 cm. for 4['1,2- bis(difluoramino)ethyl] 1,3-dioxolane; 13.0 cm. for 4,5- bis[1,=2-bis(difiuoramino)ethyl] 1,3-dioxolane; and 22.5 cm. for 2,4,5-tris[ l,2-bis'(difluoramino)ethyl]-1,3-dioxolane. All three compounds were not static-sensitive; they were not fired by a 77,500 man-equivalcnt-volt charge (1 man-equivalent-vOlt:energy of a condenser of 0.003 microfarad capacitance charged to a potential of 1 volt).

The invention has been described in detail in the foregoing. It will be apparent to those skilled in the art that many variations are possible without departure from the scope of the invention. We intend, therefore, to be limited only by the following claims.

werein X X and X are each independently selected from the group consisting of 6 and a)n 1'( 2) i( 2) a) no more than two of X X and X being CH and 5 wherein the R s and R s are independently selected from the group consisting of H and 1- to S-carbon alkyl.

2. A compound of claim 1 wherein X X and X bear 1 to 4 exocyclic carbon atoms.

3. A compound of claim 2 represented by the formula: H NF: NF; HC -H 4. A compound of claim 2 represented by the formula:

H H NF: NF:

5. A compound of claim 2 represented by the formula:

7. A process for the preparation of the compounds of claim 1 which comprises reacting, at a temperature of 75 to 250 C., tetrafiuorohydrazine with 1,3-dioxolane of the formula no more than two of X X and X being OH and wherein the Rfs and R s are independently selected from the group consisting of H and 1- to 3-carbon alkyl.

References Cited UNITED STATES PATENTS 3,346,643 10/1967 Reed 260-3409 X NICHOLAS S. RIZZO, Primary Examiner.

J. H. TURN'IPSEED, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,394,148 July 23, 1968 Robert K. Armstrong et a1 It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 52, the right-hand portion of the formula should appear as shown below:

CH-C(R )=CR (R2) Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Pz'itents Attesting Officer WILLIAM E. SCHUYLER, JR. 

1. A COMPOUND REPRESENTED BY THE FORMULA
 7. A PROCESS FOR THE PREPARATION OF THE COMPOUNDS OF CLAIM 1 WHICH COMPRISES REACTING, AT A TEMPERATURE OF 75 TO 250*C., TETRAFLUOROHYDRAZINE WITH 1,3-DIOXOLANE OF THE FORMULA 